This invention relates generally to data processing port apparatus and more particularly to a communication controller including a method and apparatus for adapting to different communication signal frequencies.
Since programmable terminals and peripherals today each have different operating parameters, data processing systems generally implement the programmable terminals and peripheral controllers by using an interface adapter designed especially for each terminal and/or controller to connect to the processing unit. The processing unit uses a single common interface standard to which all peripheral devices must adapt through the use of these special interface adapters. The interface adapter logic is unique to the peripheral device type. Each adapter logic samples the incoming signals from the peripheral device according to a timing device, generally a pulse delay circuit, and retransmits the received data information to the data processing system at the signal frequency required by the system. Similarly, on the transmit of data information, the data processing system sends the data information to the adapter which in turn buffers the data information and retransmits the data information at the frequency required by the peripheral device.
In the consideration of interface requirements for a general purpose controller, the first concept is to create a single common interface standard to which all peripheral devices must adapt through the use of special device interface electronics. However, if a single common interface is to be established, a fixed value for each of the parameters must be selected. Obviously, if this is done, many devices will have to be compromised because a common interface cannot be found which exactly suits all devices.